Shear Resistant Printing Ink Vehicles

ABSTRACT

The specification describes a process for making gelled ink resins which exhibit improved properties such as lower viscosity under low shear and less viscosity decrease with increasing shear. In a preferred embodiment, a rosin-based or hydrocarbon-based resin is mixed with an organic solvent and reacted with a polyamine reactant, such as melamine-formaldehyde resin or hexamethylene diamine, under conditions sufficient to produce a substantially covalently cross-link gelled resin. The resulting gelled resin resists viscosity breakdown under high shear conditions and may be used directly for making ink compositions, obviating the need for further gelation and avoiding the use of conventional organo-metallic gelling agents.

CROSS-REFERENCE TO RELATED APPLICATION

This application is filed pursuant to Provisional Application No.60/619,624 filed on Oct. 18, 2004.

FIELD OF THE INVENTION

The present invention relates generally to high viscosity vehiclecompositions for inks and to methods for making viscous ink vehicles.More particularly, the invention relates to an in situ process formaking shear resistant vehicles which exhibit improved rheologicalperformance characteristics for use in lithographic printing presses.

BACKGROUND OF THE INVENTION

Conventional rosin and hydrocarbon-based resins are prepared asrelatively low viscosity resins in stirred reaction vessels. Such resinsare usually highly branched and possess very broad molecular weightdistributions. The product may even contain some fraction of crosslinkedgelled structures, but this fraction is typically limited in quantity byvirtue of the inability of a stirred tank vessel to handle the very highmolten viscosity and non-Newtonian behavior that normally accompaniesthe presence of a gelled resin structure.

Lithographic ink vehicles or varnishes may be prepared from existingresins by dissolving/dispersing the resins in lithographic ink solventsand then subjecting the mixture to a so-called “gelling” reaction usingan aluminum-based gelling agent. The role of the aluminum compound inthe preparation of lithographic ink vehicles has typically been that ofcontrolling the rheological properties of the ink vehicle. Knownaluminum gelling compounds for use in preparing ink vehicles may beclassified as: 1) aluminum soaps, 2) aluminum alkoxides, 3) chelatedalkoxides and 4) oxyaluminum acylates. However, aluminum compoundsrequire the generation or existence of an aluminum hydroxylfunctionality to form the ultimate rheology or gel structure. Theresulting gel structure is the result of relatively weak coordinatecovalent or hydrogen bonding of the aluminum hydroxyl species with thebinder resin system.

Since the coordinate covalent and hydrogen bonds formed with thealuminum gelling agents are relatively weak bonds, typically only about5 to 10% as strong as covalent bonds, the gel structure afforded by suchbonds is substantially degraded under the high shear conditionsassociated with modern lithographic printing. While some degree ofthixotropic behavior is important for successful printing, there arelimits to the degree of viscosity changes which can be tolerated beforeunwanted side effects emerge. Modern high speed printing presses rapidlydegrade conventional ink vehicles to a significant degree. Oneconsequence of the loss of viscosity in an ink vehicle is thedevelopment of misting, which is more pronounced in high speed pressesleading to potential losses in print quality and degradation of the workenvironment. Misting may occur as a result of ink shear caused by highpress speeds thereby forming minute droplets or mists of ink. Inks whichmaintain higher viscosities under high shear printing conditions areless likely to mist.

Yet another undesirable aspect of the use of gelling agents is that suchagents are typically the most expensive ingredient in the varnishformulation on a weight percent basis. Hence, the use of organo-aluminumgelling agents presents a definite economic liability.

Additionally, the lithographic printing industry is shifting to the useof higher molecular weight/higher solution viscosity “self structuring”ink resins to improve the press performance of inks during high speedpress operations. New generation lithographic printing presses arecapable of achieving printing speeds in excess of 3000 feet/minute. Inorder for these ink vehicles to be effective in high speed printingpresses, increased shear resistance of the vehicles with the printingequipment is important.

Japanese patent application JP5-171089 is directed to ink varnisheswhich exhibit high gloss and improved setting and drying properties as aresult of crosslinking a portion of the polar groups of the binder resinbefore the resin is gelled with a metal gelling agent. The agents usedto reduce the number of polar groups in the resin are certain aminocompounds; preferably melamine resin or benzoguanamine resin containingat least one functional group selected from methylol, alkoxy and iminogroups, and the reaction is conducted below the softening point of thebinder resin and before all of the resin is dissolved. The gellationreaction is conducted separately from the crosslinking reaction once thepolar groups have been sufficiently cross-linked.

U.S. Pat. No. 5,763,565 discloses a process for making gelled ink resinswith improved properties. In one embodiment a rosin-based orhydrocarbon-based resin is mixed with an organic solvent and reactedwith a crosslink agent under conditions sufficient to produce asubstantially covalently cross-linked gelled resin.

A consequence of the loss of viscosity of an ink resin resulting fromexcessive shear is a loss of print sharpness. When a gelled ink resin issheared to the extent that flow becomes significant, the printed dot isdiffused thereby yielding excessive “dot gain” or poor print quality.

Because of the trend toward higher speed printing presses and thecontinuing need to improve the ink application process and printquality, there continues to be a need for improved resins for use as inkvehicles in the printing industry and improved processes for making theresins. An object of the invention is to provide shear resistant inkvehicle compositions which reduce misting and dot gain on high speedprinting machines.

Still another object of the invention is to provide an in situ processfor making shear resistant vehicle compositions of the characterdescribed with readily available, relatively inexpensive materials.

Another object of the invention is to provide a process for makingviscous shear resistant vehicle compositions which enables improvedcontrol over the properties of the resins and which enables improveduniformity in the properties of large quantities of resin.

Yet another object of the invention is to provide a process for makingresin compositions for high speed printing applications which maintaintheir viscosity even under the vigorous conditions associated with highspeed printing.

An additional object of the invention is to provide a process for makingshear resistant vehicles of the character described which is costeffective and uncomplicated and does not require the use of highlyspecialized or complicated equipment.

SUMMARY OF THE INVENTION

With regard to the forgoing and other objects, the present invention isdirected to a viscous ink vehicle and an in situ process for making ashear resistant ink vehicle having relatively low viscosity at low shearrates and maintaining a relatively large percentage of its low shearviscosity under higher shear conditions. According to one aspect of theinvention, a process is provided for making a shear resistant vehiclewhich comprises mixing a rosin- or hydrocarbon-based resin with anorganic solvent and a polyamine and/or polyamino alcohol crosslinkingagents such as melamine formaldehyde reaction products, ureaformaldehyde reaction products or a compound having two or moresecondary or tertiary amine groups to provide a reaction mass and thenheating the mass under conditions sufficient to produce a substantiallycovalently cross-linked viscous vehicle which exhibits significantlyincreased viscosity at high shear rates as compared to the uncrosslinkedresin solution, or solutions made with aluminum gelling agents, e.g.,improved shear stability against viscosity loss and elasticitydegradation from mechanical and thermal stresses imposed during its usein high speed printing machines.

Shear resistant vehicle compositions produced by the method of theinvention have been found to provide stable vehicles for varnish and inkformulations even under high shear conditions. Accordingly, inkcompositions containing a significant portion of the shear resistantvehicles made by the process of the invention have significantlyimproved misting and dot gain characteristics because they are able tomaintain their viscosity and favorable elasticity properties even whensubjected to severe mechanical and thermal stresses, whereas resinformulations that rely on the addition of aluminum gellants tend to losetheir viscosity and elasticity properties under such conditions.

Another advantage of the process of the invention is that shearresistant vehicles may be prepared without significant degradation ofthe resin because the crosslinking reaction takes place at reasonabletemperatures in situ in the solvent. Current practice for making highviscosity resins tends to induce degradation due to high temperaturesrequired to “liquefy” the resins so that they can be dissolved in an inksolvent. The present invention overcomes this problem by firstdissolving a relatively low molecular weight resin in an ink solvent attemperatures which do not induce significant degradation of the resinand then crosslinking the resin in situ in the solvent. As used herein,“shear resistant vehicle” refers to a viscous mixture of highlycross-linked resin with solvent dispersed therein so as to swell thecross-linked vehicle. Hence, the composition is not a true “solution” asthis term is generally understood; however, the term “solution” is usedherein for convenience.

According to another aspect of the invention, a process is provided formaking shear resistant vehicles which comprises a) dissolving a resinselected from the group consisting of rosin- and hydrocarbon-basedresins optionally in mixtures of one or both with other resins used ininks such as phenolic and alkyd resins in a solvent to provide areaction mixture, and b) heating the reaction mixture at a temperaturein the range of from about 120 to about 200° C. in the presence of acrosslink agent in an amount which is effective to induce formation ofsignificant covalent cross-link bonds in the resin, therebysubstantially increasing the viscosity of the resin solution. Theprocess enables the production of viscous shear resistant vehicles whichare compatible with organic ink solvents and which maintain theirrheological properties (viscosity) even under high shear conditions.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a shear resistant ink vehicle andto a process for making a shear resistant vehicle in situ whichcomprises mixing a rosin- or hydrocarbon-based resin optionally inmixtures of one or both with other ink resins such as phenolic or alkydresins with a high boiling organic solvent and a polyamine crosslinkingagent such as melamine formaldehyde reaction products, urea formaldehydereaction products or polyamines and/or polyamino alcohols to provide areaction mass. The reaction mass is heated under conditions sufficientto produce a substantially covalently cross-linked gelled resin solutionwhich exhibits improved structural stability under mechanical andthermal stresses imposed during high speed printing.

As used herein in relation to the term “resin”, the terms “rosin-based”and “hydrocarbon-based” refer to and include any of the functionalizedrosin-based resins used in ink manufacturing as well as the neutral andfunctionalized cyclic and dicyclic unsaturated hydrocarbon resincompounds derived from hydrocarbon feeds containing from about 5 toabout 15 carbon atoms, which also find wide usage in ink making.

The term “rosin” as used herein will be understood to include gum rosin,wood rosin, and tall oil rosin. Rosin is derived from pine trees(chiefly Pinus palustris and Pinus elliottii). Gum rosin is the residueobtained after the distillation of turpentine from the oleoresin tappedfrom living pine trees. Wood rosin is obtained by extracting pine stumpswith naphtha or other suitable solvents and distilling off the volatilefraction. Tall oil rosin is a co-product of the fractionation of talloil which in turn is a by-product of the wood pulping process. Theprinciple constituents of rosin are rosin acids of the abietic andpimaric types. The acids usually have the general formula C₁₉H₂₉ COOHwith a phenanthrene nucleus. A preferred rosin for use in the presentinvention is tall oil rosin.

Rosin in its natural state has limited use in inks. Its main use is as araw material for producing chemically modified rosin derivatives forvarious end uses. Important modified rosin and rosin derivatives used inprinting ink manufacturing are polymerized or dimerized rosin and estersthereof, metallic resinates, phenolic and/or maleic/fumaric modifiedrosins and their esters, and ester gums.

Important cyclic and dicyclic unsaturated hydrocarbon monomer feedstreams which contain from about 5 to about 15 carbon atoms includecyclopentadiene and/or dicyclopentadiene (DCPD), and their codimers withC4 and C5 dienes such as butadiene and piperylene. Inexpensivecommercially available DCPD concentrates typically contain from about 40wt. % to about 90 wt. % DCPD and therefore are most preferred, althoughvery high purity DCPD which is blended with olefinic modifier compoundsmay also be used.

Olefinic modifier compounds which may be used with the cyclic anddicyclic unsaturated olefins include ethylene, propylene, butadiene,styrene, alpha-methyl styrene, vinyl toluene, indene, 1,3-pentadiene,isobutylene, isoprene, 1-butene, 1-hexene, 1-octene, limonene,alpha-pinene, beta-pinene, various acrylates and mixtures of thesecompounds. The olefinic modifier compound(s) is typically used in anamount ranging from about 0% to about 35% by weight based on the totalweight of cyclic and dicyclic unsaturated olefin and modifier compound.

In addition to the use of olefinic modifiers compounds, the hydrocarbon-and rosin-based resins may be modified with distilled tall oil fattyacid, dimerized fatty acid, vegetable oils, phenolic species, maleicanhydride or fumaric acid and combinations thereof. The foregoingmodifier species may be added before, during or after the hydrocarbon-or rosin-based resin is gelled. In addition, esterification of the acidmodified resins with polyols such as pentaerythritol and/or glycerinemay be conducted to further modify the hydrocarbon- or rosin-based resinbackbone.

Any of the foregoing modified rosins, rosin derivatives and estersthereof, or cyclic and dicyclic unsaturated olefins derived and/ormodified/esterified resins may be used as the “precursor” resin for themethods of the invention. Higher molecular weight/higher solutionviscosity resins are most preferred with solution viscosities in therange of from about Z2.0 to about Z10 at 25° C. measured on one gram ofresin dissolved in two grams of alkali refined linseed oil according tothe Gardener Holt bubble tube test method. Preferred precursor resinshave a softening point in the range of from about 145 to about 180° C.and an acid number of no more than about 25. These higher molecularweight/higher solution viscosity resins are typically branched but areessentially not crosslinked. With higher molecular weight resins, theamount of crosslinking agent needed to produce the shear resistantvehicles by the process of the invention is typically reduced, thoughthe chemical characteristics of the resin may affect the amount ofcrosslink agent required.

Solvents which may be used to prepare the vehicles of the inventioninclude vegetable oils such as linseed or soybean oil, hydrocarbonsolvents such as aliphatic and aromatic solvents and lithographic inksolvents. A preferred solvent is an organic solvent, most preferably ahigh boiling organic solvent which has a boiling point in the range offrom about 220 to about 310° C. For rosin-based or hydrocarbon-basedresins, high boiling aliphatic solvents such as MAGIESOL (47, 470, 4700,N40HT, 500 or 520) which are commercially available from Magie BrothersOil Company, Division of Pennzoil of Franklin Park, Ill. and EXXPRINT(283D, 314A, 588D or 705A) which are hydrocarbon oils available fromExxon Chemical Company of Houston, Tex. are preferred. The MAGIESOLsolvents have a Kauri butanol value of from about 24 to about 27, ananiline point in the range of from about 75 to about 85° C. and adistillation range of from about 240 to about 280° C. EXXPRINT 283D hasa Kauri butanol value of 25, an aniline point of 84° C. and adistillation range of 250 to 268° C.

The amount of solvent charged to the reaction vessel is related to theamount of crosslinked resins in the composition. Typically, the solventwill be charged in an amount that results in a resin compositioncontaining from about 0.7 to about 1.5 parts by weight of solvent perpart of resin charged.

Batch reactions, reaction times may range from about 20 or 30 minutes or1 to about 8 hour or more; more desirably from 20 or 30 minutes to 2 or3 hours. Since the cross-linking reaction is rapid, a continuous orsemi-continuous process may also be used to prepare the shear resistantvehicles. Because the crosslinking reaction is conducted in the presenceof an ink solvent, the resulting highly viscous covalently crosslinkedproduct made in the reaction vessel already contains all of theimportant components of an ink vehicle composition suitable for highspeed printing machines, such as lithographic printing presses.

A key feature of the process of the invention is the formation ofcovalent cross-link bonds in the vehicle composition. In accordance withthe invention, polyamine compounds which may be used to induce formationof this bonding may be selected amine formaldehyde reaction productswith number average molecular weights from about 100 or 150 to about4000 or 5000 such as from melamine formaldehyde reaction products, ureaformaldehyde reaction products; or polyamine compounds and/or polyaminoalcohol compounds with 2 or more amino groups having molecular weightsfrom 50 to about 4000 or 5000 a few which have been found to producevehicles which exhibit superior solvency properties in lipophilicsolvents as compared to high viscosity resins made using conventionalnon-metal crosslink agents.

In several embodiments, it is desirable that the number averagemolecular weight of the crosslinkers be below 2000 grams/mole and moredesirably below 1000. The preferred crosslink agents are melamineformaldehyde reaction products, urea formaldehyde reaction products,polyalkylene polyamine compounds and/or polyamino alcohols orcombinations thereof. The polyamine or polyamino alcohols are desirablypredominantly (by weight) comprised of carbon, hydrogen, and nitrogenatoms. They may include oxygen atoms, especially in the alcohols, andother heteroatoms in small percentages.

Desirably, the percentage of atoms other than carbon, hydrogen, andnitrogen are less than 20 wt. % of the crosslinking compounds and moredesirably less than 10 or 15 wt. % of the crosslinking compounds. In oneembodiment, it is preferred to have polyamines with a predominancenumerically of secondary or tertiary amine groups as compared to primaryamine groups. In another embodiment, it is preferred that at least 80%of all amino groups are secondary or tertiary amino groups. In oneembodiment, it is preferred to that the polyamine compounds used forcrosslinking have at least 3 amino groups per molecule. In anotherembodiment, it is preferred that the polyamine compound used ascrosslinking agent have on average at least 4 amino groups per molecule.

The polyamines and polyamino alcohols may be cyclic, aliphatic oraromatic, although aliphatic amines are preferred, with an exceptionbeing the melamine formaldehyde crosslinkers which are preferred inseveral embodiments. In one embodiment, it is desirable that thepolyamine crosslinkers have a boiling point at one atmosphere pressureof above 80° C., and in another embodiment the boiling point is above1001° C.

To form covalent crosslink bonds in the precursor vehicle, the amount ofpolyamine crosslink agent may range from about 0.5 wt. % to about 15 wt.%, preferably from about 1.0 wt. % to about 5.0 wt. %, and mostpreferably from about 1.0 wt. % to about 3.5 wt. % when using polyaminesor polyamino alcohols that are free of formaldehyde based reactionproducts and from about 2 to about 6 wt. % when using urea or melamineformaldehyde type of crosslinkers based on the total weight of resin andcrosslink agent introduced to the reaction vessel.

The resin, solvent and crosslink agent may be added to the reactionvessel in any order or essentially simultaneously, provided the reactionmass components are maintained under stirred reaction conditions for aperiod of time at a suitable reaction temperature so that a gelled resinhaving a desired viscosity is produced. It is preferred, however, tofirst charge the reaction vessel with the solvent(s), under agitationadd the resin(s), heat the solvent(s) and resin(s) to a temperature inthe range of from about 120 to about 220° C., preferably from about 150to about 200° C. The crosslink agent may be added to the reaction vesselall at once or incrementally over time until the target viscosity isobtained.

It is important that the reaction mass containing solvent, resin andcrosslink agent be thoroughly mixed while being heated. During themixing and heating, a crosslink reaction occurs with the resin,providing covalent crosslink bonds in the resulting product. Once thedesired viscosity of the shear resistant resin is obtained, the reactionis terminated by cooling the reaction mass to about 100° C. or less. Thereaction product containing crosslinked vehicle is then discharged fromthe reaction vessel by gravity flow or pumping. Because a solvent isused to prepare a shear resistant vehicle, no special equipment isneeded to stir the solution during reaction or to pump the solution fromthe reaction vessel once the reaction is complete.

In general, the crosslinking reaction need not be conducted under aninert gas atmosphere, however, such an inert gas atmosphere may bebeneficial for some resins and may aid in controlling excessive colordevelopment and for fire suppression. Furthermore, the reaction may beconducted under atmospheric, subatmospheric or superatmospheric pressureconditions. Atmospheric pressure is particularly preferred. Regardlessof the pressure in the reaction vessel, it is important that thereactants be maintained at a sufficiently high temperature with intensemixing for a period of time sufficient to achieve the desired level ofcrosslinking of the components in the reaction product.

Due to the in situ formation of crosslinked vehicle, the productproduced by the process of the invention already contains a solvent,preferably a lithographic solvent such as MAGIESOL 47/470, EXXPRINT283D, linseed oil or soybean oil, typically in an amount ranging fromabout 10 to about 50 wt. % solvent based on the total weight of theresin/solvent mixture. Accordingly, the viscous reaction product isready for direct addition to the final ink composition with the otherink components, i.e., pigment, wax compounds and the like.

Further aspects of the invention will now be illustrated by reference tothe following non-limiting examples.

EXAMPLE 1 Vehicle Example A

Raw Material % by wt. Conventional Important Alkyd resin 5 X Vegetableoil 5 X Middle boiling ink solvent 37.7 X High boiling ink solvent 12 XX Phenolic resin 12.4 X Rosin ester resin 16 X Hydrocarbon resin 9.4 XMelamine formaldehyde 2.5 X reaction products X

-   A Charge alkyd, vegetable oil, middle and high boiling ink solvents-   B Under agitation, add rest of resins-   C Heat mixture to 360° F. (182° C.)-   D Add (melamine formaldehyde reaction products), heat to 380° F.    (193° C.) and hold 30 minutes.-   E Adjust with middle boiling ink solvent as needed.

(Step D is the innovative step, along with using a higher thanconventional temperature to maximize the kinetics of the crosslinkingwith the melamine-formaldehyde resin) Vehicle Example B

Raw Material Code % by wt. Conventional Important Alkyd resin 5 XVegetable oil 5 X middle boiling ink solvent 36.9 X High boiling inksolvent 13 X Phenolic resin 12.7 X Rosin ester resin 16.5 X Hydrocarbonresin 10 X Polyamine 0.9 X

A Charge alkyd, vegetable oil, middle and high boiling ink solvents BUnder agitation, add rest of resins C Heat mixture to 340° F. (171° C.)D Add polyamine, hold 30 minutes. E Adjust with middle boiling inksolvent as needed. (Step D is the innovative step, along with using ahigher than conventional temperature to maximize the kinetics of thecrosslinking with the polyamine/polyamino alcohol.

We tested the materials as vehicles and in ink formulations. Viscositymeasurement tests included rotational rheometric measurements of varyingshears from 1 sec−1 to 100 sec−1, and oscillatory measurements from 1 hzto 100 hz. Additionally, the inks were printed at a press trial at 1800ft./minute on a “Harris M2000 Sunday Press” printing press.

The press trial showed the inks made with Vehicle Example A and VehicleExample B were easier to load into the ink fountains because theyexhibited less viscosity (this is a low shear operation), yet resistedviscosity reduction when sheared on the press by exhibiting less “dotgain” than the conventional ink while not losing or detracting fromgloss or density. Dot gain refers to the spreading or enlarging of theprinted dot which negatively affects printing fidelity and quality.

Flow Viscosities of Inks

Viscosity Viscosity (Pa · s.) @ 100 sec−1 (Pa · s.) @ 5 sec−1 Highervalues offers less Lower values offers easier dependence of viscosity toInk processing at low shear shear rates Control 511 21 Standard AVehicle 353 35 Example A Vehicle 194 28 Example B

Oscillatory Viscosities of Inks

η* (complex viscosity) G′ G″ Tan Δ Ink 0.1 hz/100 hz 40 hz 40 hz 40 hzControl Std A 908/48 9,000 14,800 1.64 Vehicle 368/43 7,200 13,500 1.87Example A Vehicle 246/38 5,200 11,500 2.18 Example B

Print Results

Gloss Ink Density 60°/85° Dot gain Control Std A 1.33 32/49 15.5%Vehicle 1.38 34/49 13.1% Example A Vehicle 1.38 35/50 13.2% Example B

Control Std. A is a proven, conventional vehicle in current marketplaceusage which we used as a standard test vehicle.

The foregoing description of certain embodiments of the presentinvention has been provided for purposes of illustration only, and it isunderstood that numerous modifications and alterations may be madewithout departing from the spirit and scope of the invention as definedin the following claims. The embodiments described herein are the bestmode known to applicant for practicing the invention, but it will beunderstood that other ways of producing high viscosity ink resinsaccording to the claims are encompassed by the invention.

1. A composition for an ink vehicle which comprises a reaction productfrom mixing a rosin- or hydrocarbon-based resin with an organic solventand a polyamine crosslinking agent to provide a reaction mass andheating the reaction mass under conditions sufficient to produce asubstantially covalently cross-linked vehicle which exhibits lower lowshear viscosity and equal or greater high shear viscosity as compared tothe uncrosslinked vehicle or aluminum gelled vehicle and has improvedstability against viscosity loss and elasticity degradation frommechanical and thermal stresses imposed during its use in high speedprinting machines.
 2. The composition of claim 1 wherein the reaction isconducted under a nitrogen atmosphere.
 3. The composition of claim 1wherein the resin is a rosin-based resin comprising an ester of modifiedrosin.
 4. The composition of claim 1 wherein the resin is a rosin-basedresin which comprises a maleic modified rosin ester resin having asoftening point in the range of from about 150 to about 170° C., an acidnumber of no more than about 25, a solution viscosity in the range offrom about Z5.0 to about Z7.0, and a M47 tolerance of from about 15 toabout 30 mLs.
 5. The composition of claim 1 wherein the resin is arosin-based resin which comprises a phenolic modified rosin ester resinhaving a softening point in the range of from about 150 to about 180°C., an acid number of less than about 25, a solution viscosity rangingfrom about Z5.5 to about Z8.0, and a M47 tolerance of at least about 10mLs.
 6. The composition of claim 1 wherein the resin is ahydrocarbon-based resin which comprises a functionalized cyclic ordicyclic unsaturated hydrocarbon resin derived from a hydrocarbon feedcontaining from about 5 to about 15 carbon atoms, having a softeningpoint of from about 145 to about 170° C., a solution viscosity rangingfrom about Z2.5 to about Z5.5 based on a 50 wt. % solution in ink oiland a M47 tolerance ranging from about 4 to about 15 mLs.
 7. Thecomposition of claim 1 wherein the crosslink agent is selected from thegroup comprising melamine formaldehyde reaction products or ureaformaldehyde reaction products.
 8. The composition of claim 1 whereinthe crosslink agent is a polyamine and/or polyamino alcohol other thanmelamine formaldehyde reaction products or urea formaldehyde reactionproducts.
 9. The composition of claim 1 wherein the crosslink agent is aformaldehyde free polyamine and/or polyamino alcohol.
 10. Thecomposition of claim 9 wherein the resin and polyamine and/or polyaminoalcohol compound are reacted until a solution viscosity in the range offrom about 100 to about 1000 poise at 25° C. is obtained.
 11. Thecomposition of claim 10 wherein the amount of polyamine compound rangesfrom about 0.5 to about 10 wt. % based on the total reaction massweight.
 12. The composition of claim 1 wherein the organic solvent is ahigh boiling organic solvent having a boiling point in the range of fromabout 220 to about 310° C.
 13. A lithographic ink formulation comprisingfrom about 30 to about 80 wt. % of the resin composition of claim 1,from about 0 to about 25 wt. % pigment and from about 1 to about 15 wt.% ink oil.
 14. A process for making a high viscosity gelled ink resincomposition which comprises mixing a rosin- or hydrocarbon-based resinwith an organic solvent and a polyamine crosslinking agent to provide areaction mass and heating the reaction mass under conditions sufficientto produce a substantially covalently cross-linked vehicle which ischaracterized by significantly increased viscosity as compared to theuncrosslinked resin solution and has improved stability againstviscosity loss and elasticity degradation from mechanical and thermalstresses imposed during its use in high speed printing machines.
 15. Theprocess of claim 14 wherein the reaction is conducted under a nitrogenatmosphere.
 16. The process of claim 14 wherein the resin is arosin-based resin comprising an ester of modified rosin.
 17. The processof claim 14 wherein the resin is a rosin-based resin which comprises amaleic modified rosin ester resin having a softening point in the rangeof from about 150 to about 170° C., an acid number of no more than about25, a solution viscosity in the range of from about Z5.0 to about Z7.0,and a M47 tolerance of from about 15 to about 30 mLs.
 18. The process ofclaim 14 wherein the resin is a rosin-based resin which comprises aphenolic modified rosin ester resin having a softening point in therange of from about 150 to about 180° C., an acid number of less thanabout 25, a solution viscosity ranging from about Z5.5 to about Z8.0,and a M47 tolerance of at least about 10 mLs.
 19. The process of claim14 wherein the resin is a hydrocarbon-based resin which comprises afunctionalized cyclic or dicyclic unsaturated hydrocarbon resin derivedfrom a hydrocarbon feed containing from about 5 to about 15 carbonatoms, having a softening point of from about 145 to about 170° C., asolution viscosity ranging from about Z2.5 to about Z5.5 based on a 50wt. % solution in ink oil and a M47 tolerance ranging from about 4 toabout 15 mLs.
 20. The process of claim 14 wherein the crosslink agent isselected from the group comprising melamine formaldehyde reactionproducts or urea formaldehyde reaction products.
 21. The process ofclaim 14 wherein the crosslink agent is a polyamine and/or polyaminoalcohol other than melamine formaldehyde reaction products or ureaformaldehyde reaction products.
 22. The process of claim 14 wherein thecrosslink agent is a formaldehyde free polyamine and/or a polyaminoalcohol.
 23. The process of claim 22 wherein the resin and polyaminecompound are reacted until a solution viscosity in the range of fromabout 100 to about 1000 poise at 25° C. is obtained.
 24. The process ofclaim 23 wherein the amount of polyamine compound ranges from about 0.5to about 10 wt. % based on the total reaction mass weight.
 25. Theprocess of claim 14 wherein the organic solvent is a high boilingorganic solvent having a boiling point in the range of from about 220 toabout 310° C.
 26. A process for making a high viscosity gelled resinwhich comprises: charging a stirred reaction vessel with a high boilingorganic solvent; feeding ink resin to the solvent with stirring to forma reaction mass containing from about 30 to about 60 wt. % resin;heating the reaction mass to a temperature within the range of fromabout 150 to about 200° C.; adding a sufficient amount of a heatreactive polyamine and/or polyamino alcohol crosslinking agent to thereaction mass while maintaining the reaction temperature in the range offrom about 150 to about 220° C. to obtain a partially crosslinkedvehicle.
 27. An ink vehicle comprising the gelled resin of claim 1.